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Thread: Thread for my general questions regarding training

  1. #11
    Grouper
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    Nice thread
    "God is at the bottom of the sea and
    I dive to find him." Enzo Maiorca

  2. #12
    Instructor, Technical & Cave Diver "Forum Admin" TommyB's Avatar
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    Quote Originally Posted by bennerman View Post
    Are these correct?

    How a wetsuit works: The suit traps a layer of water between the suit and the diver. This water is then heated by the body's natural heat to a level that is more comfortable for the diver.

    How a drysuit works: The suit is made water tight and filled with air, keeping the diver dry. A special undergarment is warn that is designed to keep the diver warm.
    Yes
    Yes and no.. can be filled with air / argon / etc. For cold temps most use argon.

    quick course

    Dry suit - Wikipedia, the free encyclopedia

    Wetsuit - Wikipedia, the free encyclopedia
    Tommy Burchfield Naui/TDI/SDI
    if ( $clue == \'none\' ) { read ( sig & avatar rules | forum rules ) && search ( forums | google ) }
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  3. #13
    Shark
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    I have that written down as "filled with a gas" on the actual worksheet
    Rock on, go big or go home, hit the ground running, hang in there kitty... don't eat the yellow snow...

  4. #14
    Shark
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    This doesn't mention what to do against a current encountered on the bottom, only what to do when you encounter one on the surface... any ideas?
    Rock on, go big or go home, hit the ground running, hang in there kitty... don't eat the yellow snow...

  5. #15
    Quote Originally Posted by bennerman View Post
    This doesn't mention what to do against a current encountered on the bottom, only what to do when you encounter one on the surface... any ideas?
    Continue reading the manual and watching the video. The answer is in there, I promise.

  6. #16
    Shark
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    if you say so :P
    Rock on, go big or go home, hit the ground running, hang in there kitty... don't eat the yellow snow...

  7. #17
    Shark
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    Ok, so for table one of dive tables, you get the pressure group by taking the depth (or next highest interval of depth), looking at the time below (or next highest interval), and the letter across is the pressure group? And for table two, you take the the group you were in when you got out of the water, move to the right to find the time you have spent out, and then the letter below is your new pressure group. Is that correct?
    Rock on, go big or go home, hit the ground running, hang in there kitty... don't eat the yellow snow...

  8. #18
    Megalodon
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    You pretty much have he gist of it. The hardest part of the tables is the repetative dive. Here's a way o think about it:

    When you start your first dives, your body is 100% saturated with Nitrogen (N) and oxygen for that matter-but that's immaterial for the tables-at the water surface. Even though you have N is your system , call it your baseline of zero for excess N.

    When you dive, you add pressure which adds N to your system at a steady rate faster or slower depending on the body tissue but again this is background for advanced stuff later. The longer you stay down the more N you absorb into body tissues. You're not doing deco dives so there is a point that at a given depth, you have enough N in your tissues that anymore will cause microbubbles in tissue if you stay any longer. This is the No Decompression limit for that depth (NDL).

    Being a good diver, you have planned your dive and you head to the surface before your NDL. Your N loading for that depth at the end of your dive is represented by a letter. The higher the letter (M vs. L vs. C) the more N that's in your system. This is the right side of table 1. Remember this letter

    When you get to the surface and start you surface interval, you are off-gassing that excess N. It leaves the body at a steady rate. In theory, it takes 12 hours to fully off gas. Some say 24, but for purposes of the tables, it's 12 hours. You get credit for the off-gassed N you lost while resting on the surface. But if you dive again in less than 12 hours, you still have N in your system from the previous dive. This is table 2. Start with your End of dive pressure group letter and follow is horisontally to the right until you find the time span that meets the length of your SI. This is your pressure group at the end of the surface interval - remember this letter.

    That amount of additional Nitrogen still in your system is effected differently depending on the depth of your next dive. So you have to know the depth for the second dive. Go to the back side and find the planned depth on the left side (let's say 50' )follow it horizontally until your in line with the vertical column that has your end of SI press group at the top ( "C"). On the PADI Tables, the TOP white box is residual nitrogen time - this is the amount of nitrogen still in your system from the first dive, the easiest way to show this is as the amount of nitrogen that would be in your body if it was the first dive for that amount of time. So starting your second dive, you have the same amount of N is your sytems as you did if your first dive had been to 50' for 17 minutes.

    Here's were it gets tricky: if you're 17 minutes into your first dive at 50' and your NDL is 80 minutes, you can only stay MORE 63 minutes. Since this is the second dive, you've got "C" nitrogen left in your system and it's equivient to 17 minutes of diving at 50' your Adjusted NDL for the second dive is 63 minutes. So your second dive was 23 minutes (for simplicity sake) you still had that 17 minutes if N from dive one in your sytem that didn't go away during the dive so you have to account for those 17 minutes along with you actual bottom time of 23 minutes. At the end of the second dive, the amount of nitrogen in your system is the same at 23 minutes as it would have been if this was your first dive of 40 minutes (17 min RNT and 23 minutes Actual Bottom Time or ABT- 17+23=40) remember that 40 minutes....

    At the end of dive 2, your back to table one. 50' for 40 minutes (ABT plus RNT) Since table 1 is your dive, the end of dive reptative group is "M". And you start back over. Note since you've accounted for the extra nitrogen your took with you on dive 2 from dive 1 after your SI, it's now part of dive two's Nitrogen load so you can forget about dive on and calcualte your SI and all from the 40 minutes of nitrogen from dive 2. even though it was only 23 minutes.

    Also get the table tutor from Scuba Toys: Table Tutor reviews and discounts, ScubaToys download it, install it and send joe and larry a pm with the shareware number and they'll send you the unlock code for free-save $15 us!

    I once saved a man in Wichita just to watch him dive...(inventor)

  9. #19
    Shark
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    AHA!
    Ok, the sample question is:
    First Dive: 50ft at 40 minutes, surface interval of 1 hour, and second dive of 40 ft at 60 minutes. What is my pressure group?

    So, tell me if I get this right:
    The first dive was 50ft, and then you go down to 41 minutes (being the closest number rounded up). This gives a pressure group of M. M after 1 hour turns into D. a D diving at 40 feet would have a RNT of 25 minutes. The RNT plus the ABT would be 85 minutes (25 + 60). A person in group D being under for 85 minutes at 40 minutes would be a member of group S, so the answer is S.
    Rock on, go big or go home, hit the ground running, hang in there kitty... don't eat the yellow snow...

  10. #20
    Megalodon
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    That's it. Now, give youself a 1:45 SI, your next dive is back to 50' for 30 minutes. What's your end of dive group?

    I once saved a man in Wichita just to watch him dive...(inventor)

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